1. Field of the Invention
The present invention relates to a lens dyeing method and an apparatus for producing a dyeing base body for dyeing a lens.
2. Description of Related Art
As a method for dyeing plastic (synthetic resin) spectacle lenses, a dyeing method by dipping a lens in a dyeing solution (a dip dyeing method) has been known. This method, which has been used from long ago, has disadvantages such as poor working environments and difficulty in dyeing a lens made of a high refractive material. Therefore, the inventors of the present invention proposed a dyeing method in which dyeing inks containing sublimable dyes are applied onto a dyeing base body by a printer, an ink-applied surface of the base body and a surface of the lens to be dyed are placed facing each other in noncontact relation under substantially a vacuum condition, and the base body is heated to deposit the dyes onto the lens (hereinafter, referred to as a “vapor deposition transfer dyeing method”). See U.S. Pat. No. 6,520,999B1 (EP 1249334B1, JP2001-59950A), for example.
Spectacle lenses have curvatures determined by powers. Thickness of an edge of the lens is also determined by the power. For example, a low (weak) minus power lens is small in curvature and thus a lens peripheral portion (edge) is not so thick as compared with a lens central portion. On the other hand, a high (strong) minus power lens is large in curvature and thus a lens peripheral portion (edge) is thicker than a lens central portion, resulting in a large difference between a vertical distance from the base body to the lens central portion and a vertical distance from the base body to the lens peripheral portion. If this difference in distance is large, the vapor deposition transfer dyeing method conducted by depositing dyes onto a lens to dye the lens would have a difficulty in dyeing the lens surface to be dyed with almost uniform color density. Even in sunglasses having no power, the above disadvantage likely occurs due to a difference in curvature.